This disclosure relates to a data storage system and to a method of operating the data storage system. In one embodiment, a FlashCopy® (FlashCopy is a registered trademark or trademark of International Business Machines Corporation in the United States and/or other countries.) process is used to separate frequently accessed data from less frequently accessed data using a single FlashCopy target with multiple bitmaps to reduce capacity usage.
Within a large data storage system there are likely to be multiple different types of storage media in use. The various types can be classified by a number of metrics, such as capacity, availability, performance and cost. Examples of different properties that distinguish the different classes of storage might include attachment technology (for example, SATA or FC/SCSI) drives, redundancy scheme (for example, RAID-5, RAID-1 or RAID-10), and space-saving algorithm (for example, compression, de-duplication or non-compressed). A new class of storage technology that is emerging is storage-class memory, of which Flash Memory is a preferred example. The different applications and servers that are being hosted by the storage media will have varying requirements with respect to these metrics. Each application will tend to have its own requirements, and a given application's requirements will also tend to vary over time as the demands on that application vary.